Organic EL display device

ABSTRACT

An organic EL display device includes: a lower electrode; an upper electrode; a first organic layer which is disposed between the lower electrode and the upper electrode and is formed of a plurality of layers including a light emitting layer formed of an organic material that emits light; a metal wire that extends between the pixels within the display region; and a second organic layer which is formed of a plurality of layers the same as that of the first organic layer and which comes into contact with a part of the metal wire and does not come into contact with the first organic layer. The upper electrode comes into contact with the metal wire in the periphery of the second organic layer. Accordingly, it is possible to uniformize the potential of the upper electrode without reducing the light emission area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/469,628 filed on Aug. 27, 2014. Further, this application claimspriority from Japanese application No. 2013-178680 filed on Aug. 29,2013, the contents of which are hereby incorporated by reference intothis application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic EL display device and amethod of manufacturing the organic EL display device, and morespecifically, to an organic EL display device that performs display byemitting light on a light emitting element which is a self-luminous bodydisposed in each pixel, and a method of manufacturing the same.

2. Description of the Related Art

In recent years, an image display device (hereinafter, referred to as“organic EL (Electro-luminescent) display device”) using a self-luminousbody called organic light emitting diode (OLED) is in practical use.Since the organic EL display device uses the self-luminous body, it isnot only excellent in terms of visibility and response speed, but it isalso possible to make the device thinner because an auxiliaryilluminating device such as a backlight is not required, compared to aliquid crystal display in the related art.

In a display device in which light is emitted to a side on which a lightemitting element of an insulated substrate is formed, that is, a topemission type display device, among an upper electrode and a lowerelectrode as two electrodes that sandwich an organic layer having atleast a light emitting layer as a layer, the upper electrode is anelectrode, which covers the entire surface of a display region on whichthe organic layer is formed, and is formed of a transparent conductivematerial. It is desired that the upper electrode be formed thinner inorder to improve transmittance of light. However, the thinner the upperelectrode is, the higher the resistance value is and the lower thevoltage is. Therefore, luminance unevenness easily occurs at the endportion and the center of the display region.

JP 2004-207217 A discloses that an upper electrode is brought intocontact with an auxiliary electrode in a layer which is the same as thatof a lower electrode within a display region, through a connection holeand that the resistance of the upper electrode is reduced. JP2011-221203 A discloses that an upper electrode is electricallyconnected to a conductive substrate through a connection hole within adisplay region.

SUMMARY OF THE INVENTION

Bringing the upper electrode into contact with the electrode of a metalhaving a high conductivity within the display region as disclosed in theabove JP 2004-207217 A and JP 2011-221203 A is effective for reducingthe resistance of the upper electrode and for uniformizing potential.However, in both cases, the connection hole is required for the organiclayer. Therefore, in consideration of deposition precision of theorganic layer formed using a deposition mask, it is difficult to open ahighly precise hole and a connection hole which is opened in each pixelhas a certain size. However, this reduces the area of a portion fromwhich light is emitted, thereby resulting in degradation in a contrastof the display. Particularly, in an organic EL display device having anorganic layer that covers the surface of a display region without usinga deposition mask, it is difficult to provide the connection hole withinthe display region.

The invention has been made from the viewpoint of the above-describedproblems and an object of the invention is to provide an organic ELdisplay device in which a potential of an upper electrode is uniformizedwithout reducing the light emission area.

(1) An organic EL display device includes: a lower electrode which isdisposed for every pixel disposed in a matrix shape within a displayregion and is formed of a conductive material, and in which a potentialis controlled for every pixel; an upper electrode which is disposed soas to cover the display region and is formed of the conductive material;a first organic layer which is disposed between the lower electrode andthe upper electrode and is formed of a plurality of layers including alight emitting layer formed of an organic material that emits light; ametal wire that extends between the pixels within the display region;and a second organic layer which is formed of a plurality of layers thesame as that of the first organic layer and which comes into contactwith a part of the metal wire and does not come into contact with thefirst organic layer. The upper electrode comes into contact with themetal wire in the periphery of the second organic layer.

(2) In (1), the organic EL display device may further includes: aflattening film formed of the organic material covering a circuit whichis formed on a substrate and includes the metal wire and a thin filmtransistor; and an insulating bank that covers an end portion of thelower electrode which is formed on the flattening film among the lowerelectrode, the first organic layer, and the upper electrode, andelectrically insulates the pixels. The upper electrode may come intocontact with the metal wire through a contact hole opened in theflattening film and the insulating bank.

(3) In (1) or (2), the upper electrode may continuously come intocontact with the metal wire within the display region along the metalwire.

(4) In any one of (1) to (3), the metal wire may vertically andhorizontally extend so as to surround each of the pixels within thedisplay region.

(5) In any one of (1) to (4), the first organic layer may have the samelight emitting layer in all of the pixels within the display region.

(6) A method of manufacturing an organic EL display device includes: ametal wire formation step of forming a metal wire between pixels in adisplay region in which the pixels are disposed in a matrix shape; aninsulating wire formation step of forming an insulating film using aninsulation material so as to cover the display region on the metal wire;a contact hole formation step of forming a contact hole through which atleast a part of the metal wire is exposed with respect to the insulatingfilm; an organic layer formation step of simultaneously forming a firstorganic layer which is disposed on the insulating film and is formed ofa plurality of layers including a light emitting layer formed of anorganic material that emits light, and a second organic layer which isdisposed at the bottom of the contact hole and is discontinuous to thefirst organic layer; and an upper electrode formation step of forming anupper electrode which is formed of a conductive material and which comesinto contact with the metal wire and covers the display region, afterthe organic layer formation step.

(7) In (6), the method of manufacturing the organic EL display devicemay further include: a flattening film-formation step of forming aflattening film using the organic material on the metal wire after themetal wire formation step; a flattening film contact hole formation stepof forming a contact hole through which the metal wire is exposed withrespect to the flattening film; and a lower electrode formation step offorming a lower electrode for every pixels on the flattening film. Theinsulating film formed in the insulating film formation step may be aninsulating bank that electrically insulates the pixels and the contacthole formation step may be an insulating bank contact hole formationstep performed on the insulating bank.

(8) In (6) or (7), the organic layer formation step may be a step offorming an organic layer through a deposition method and the upperelectrode formation step may be a step of forming the upper electrodethrough a sputtering method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing an organic EL display deviceaccording to an embodiment of the invention.

FIG. 2 is a view showing a configuration of an organic EL panel of FIG.1.

FIG. 3 is an enlarged view schematically showing four pixels of FIG. 2.

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3.

FIG. 5 is a view illustrating a step of forming an upper electrode whichis formed in an upper electrode contact hole.

FIG. 6 is an enlarged view schematically showing four pixels of anorganic EL display device as a modification example of the presentembodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of the invention will be described withreference to the accompanying drawings. In the drawings, the samecomponents will be denoted by the same reference numerals throughout andthe detailed description thereof will be omitted.

FIG. 1 schematically shows an organic EL display device 100 according tothe embodiment of the invention. As shown in FIG. 1, the organic ELdisplay device 100 is formed of an organic EL panel 200 which is fixedso as to be interposed between an upper frame 110 and a lower frame 120.

FIG. 2 shows a configuration of the organic EL panel 200 of FIG. 1. Theorganic EL panel 200 has two substrates which are a thin film transistor(TFT) substrate 220 and a sealing substrate 230 and transparent resin(not shown) is filled between these substrates. The TFT substrate 220has pixels 280 arranged in a display region 202 in a matrix shape. Inaddition, a driving IC (integrated circuit) 260 which is a drivingcircuit that applies a potential for electrically connecting a sourceand a drain with respect to a scanning signal line (not shown) of apixel transistor, the scanning signal line being disposed in each pixel,and applies a voltage corresponding to a gradation value of a pixel withrespect to a data signal line of each pixel transistor is mounted on theTFT substrate 220.

FIG. 3 is an enlarged view schematically showing four pixels 280 of FIG.2. In FIG. 3, in order to describe the present embodiment, only a partof electrodes is shown by a solid line in a planar view regardless ofthe lamination relation. As shown in FIG. 3, each of the pixels 280 hasan independent lower electrode 304 for every pixel 280, and anindependent lower electrode contact hole 282 for every pixel 280 inwhich the lower electrode 304 is connected to source and drainelectrodes 309 to be described later. As described below, a firstorganic layer 306 including a light emitting layer disposed on theentire surface of the display region 202, and an upper electrode 307disposed on the first organic layer on the entire surface of the displayregion are disposed on the lower electrode 304 in this order. A metalwire 284 is disposed between the pixels 280 and a second organic layer285 which has the same layer structure as that of the first organiclayer 306 is mounted on the metal wire 284. An upper electrode contacthole 287 is formed such that the upper electrode 307 and the metal wire284 are connected to each other.

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3. Asshown in FIG. 4, the TFT substrate 220 has a glass substrate 301 whichis an insulating substrate; the source and drain electrodes 309 and themetal wire 284 which are formed of a conductive material on the glasssubstrate 301; a flattening film 303 formed of an insulating material onthe source and drain electrodes 309 and the metal wire 284; the lowerelectrode 304 connected to the source and drain electrodes 309 through acontact hole which is opened in the flattening film 303; an insulatingbank 305 which covers an end portion of the lower electrode 304 andinsulates between electrodes between pixels; a first organic layer 306including a light emitting layer and a common layer such as an electroninjection layer and a hole transport layer which are formed so as tosubstantially cover the entire display region 202 on the lower electrode304 and the insulating bank 305; the upper electrode 307 which is formedso as to cover the entire display region 202 on the first organic layer306; a sealing film 308 that blocks air or water in order to prevent thefirst organic layer 306 from deteriorating; and a second organic layer285 formed on the metal wire 284. Although it is not shown in FIG. 4,the source and drain electrodes 309 are connected to the TFT, which isformed in each of the pixels 280, between the glass substrate 301 andthe flattening film 303. The light emitting layer of the first organiclayer emits light when a positive hole or an electron which is injectedthrough the lower electrode 304 and an electron or a positive hole whichis injected through the upper electrode 307 are recombined, an excitedstate is formed, and the state is transferred to a ground state.

As shown in FIG. 4, the upper electrode 307 comes into contact with themetal wire 284 disposed between the pixels 280 through the upperelectrode contact hole 287. For this reason, the upper electrode 307 ofwhich the resistance value is increased by being thinly formed withinthe display region 202 can come into contact with the metal wire 284having high conductivity within the display region 202. Therefore, thepotential of the upper electrode 307 is uniformly maintained within thedisplay region 202. The second organic layer 285 is disposed on themetal wire 284 of a region formed with the upper electrode contact hole287.

Here, the organic EL display device 100 according to the presentembodiment is an organic EL display device with a system of emittinglight with a uniform wavelength region (for example, W (white)) in theentire surface of the display region, and extracting light at awavelength region corresponding to RGB using a color filter provided inthe sealing substrate 230. However, the organic EL display device is notlimited thereto and may be an organic EL display device with a system ofemitting light at respective wavelength regions of RGB in the pixels,and extracting light without using the color filter. In this case, thefirst organic layer including the light emitting layer, and the secondorganic layer are formed by being painted in a dot shape or a stripeshape for every pixel through deposition or the like.

FIG. 5 is a view illustrating a step of forming the upper electrode 307which is formed in the above-described upper electrode contact hole 287.In the step, first, the metal wire 284 is formed in a metal wireformation step S11. Here, the metal wire 284 (not shown) can besimultaneously formed at the same step with any of a gate electrode, adrain electrode, and a source electrode of the TFT formed in each of thepixels, and other wires except for the TFT. In this case, the metal wire284 may not only be directly formed on the glass substrate 301, but mayalso be formed on an insulating film which is formed on the glasssubstrate 301.

Next, in a flattening film-formation step S12, a flattening film 303formed of an organic material such as a photosensitive organic materialis formed. In a flattening film-contact hole formation step S13, theupper electrode contact hole 287 is formed on the flattening film 303through a well-known photolithography step to expose the metal wire 284.Then, although it is not shown in FIG. 5, in a lower electrode formationstep, the lower electrode 304 is formed within the pixel 280. In aninsulating bank-formation step S14, an end portion of the lowerelectrode 304 is covered and an insulating bank 305 which insulates thepixels and is formed of an organic material or an inorganic material isformed. Subsequently, in an insulating bank-contact hole formation stepS15, the upper electrode contact hole 287 is formed in the insulatingbank 305 through the well known photolithography step to expose themetal wire 284.

The flattening film 303 can be formed by covering the entire TFT circuitformed on the glass substrate 301 and the upper electrode contact hole287 of the flattening film 303 can be simultaneously formed in the samestep as that of forming the lower electrode contact hole 282 of FIG. 4.In addition, the upper electrode contact hole 287 of the insulating bank305 can be simultaneously formed with the step of exposing the lowerelectrode 304 from the insulating bank 305.

In an organic layer formation step S16, the first organic layer 306 andthe second organic layer 285 are simultaneously formed throughdeposition. Here, the first organic layer 306 and the second organiclayer 285 are simultaneously formed through the deposition. However, anorganic material which is heated in a vacuum is adhered thereto withdirectivity. Therefore, the first organic layer 306 which is formed onthe insulating bank 305 and the second organic layer 285 which is formedon the metal wire 284 are formed as discontinuous layers (steppingstructure) by an extremely large step in the upper electrode contacthole 287. The first organic layer 306 and the second organic layer 285in the present embodiment are set to be formed through the deposition,but can be formed by a formation method such as offset printing so as tomake discontinuous layers by providing a step.

Lastly, in an upper electrode formation step S17, the upper electrode307 is formed through a sputtering method using a transparent electrodesuch as indium tin oxide (ITO) and indium zinc oxide (InZnO). Thetransparent electrode formed through the sputtering method has goodthrowing power compared to the deposition of the organic material.Therefore, the transparent electrode is adhered even to thediscontinuous portion between the first organic layer 306 and the secondorganic layer 285 and is formed as a continuous upper electrode 307coming into contact with the metal wire 284.

In a subsequent step, a sealing film is formed using SiN or a glass capwhich is a well-known step. Therefore, the detailed description thereofwill be omitted. In the present embodiment, the upper electrode contacthole 287 is set to be formed in both of the flattening film 303 and theinsulating bank 305. However, the metal wire may be formed on theflattening film 303 and the upper electrode contact hole 287 may beformed only in the insulating bank 305, for example.

As described above, in the present embodiment, the upper electrode 307can be brought into contact with the metal wire 284 having a lowresistance value on the glass substrate 301 in the display region 202.Therefore, it is possible to reduce the sheet resistance of the upperelectrode 307 and save the power consumption. In addition, partialvoltage reduction does not occur in the display region 202, andtherefore, it is possible to maintain uniformity of display.Furthermore, it is possible to bring the upper electrode 307 intocontact with the metal wire 284 without patterning the first organiclayer and the second organic layer. Therefore, it is possible tomaintain the area of the light emitting region of the pixel to be largeand to make the pixel a high definition pixel without increasing thenumber of steps. Particularly, it is possible to effectively apply theprinciple to an organic EL display device which has an organic layerincluding a light emitting layer formed on the entire surface of adisplay region 202 or a common layer. However, it is possible to applythe principle even to an organic EL display device formed of lightemitting layers mutually having different wavelength regions of emittedlight.

FIG. 6 is an enlarged view schematically showing four pixels 480 of anorganic EL display device as a modification example of the presentembodiment. Similarly to FIG. 3, in order to describe the presentembodiment, only a part of electrodes is shown by a solid line in aplanar view regardless of the lamination relation. Similarly to theabove-described embodiment, each of pixels 480 has a lower electrode 481and a lower electrode contact hole 482. Points different from theabove-described embodiment is that a metal wire 484 which is connectedto an upper electrode 407 is vertically and horizontally disposedbetween the pixels 480, and an upper electrode contact hole 487 and asecond organic layer 485 which is formed on the upper electrode contacthole 487 are also vertically and horizontally disposed along the metalwire 484. Even in this case, in order to ensure the opening ratio, it isdesirable that the area of the upper electrode contact hole 487 besmaller than or equal to 10% of the area of the lower electrode 481.

With such a configuration, the first organic layer becomes anindependent discontinuous layer (stepping structure) for every pixel480, and therefore, it is possible to suppress light emission atadjacent pixels, that is, electrical color mixture caused by leakage ofa current to the adjacent pixels, in addition to obtaining the effect inthe above-described embodiment. Moreover, the organic bank also becomesdiscontinuous for every pixel 480, and therefore, the leaked lightentering the organic bank by being emitted in a horizontal direction isnot emitted from the adjacent pixels if the leaked light does not passthe interface of many layers. Thus, it is also possible to suppressoptical color mixture.

In the present embodiment, the organic EL display device in which thesame kinds of organic layers are formed on the entire display region isdescribed. However, the organic EL display device in which organiclayers are formed for every pixel having different wave regions ofemitted light may also be used.

Various modification examples and correction examples can be conceivedby those skilled in the art in the category of the idea of theinvention. Accordingly, it is understood that the modification examplesand the correction examples also belong to the scope of the invention aslong as they have the gist of the invention.

What is claimed is:
 1. An organic EL display device comprising: a firstlower electrode in a display region; a second lower electrode in thedisplay region; an upper electrode covering the display region; a wirerunning between the first lower electrode and the second lowerelectrode; a flattening film formed of an organic material covering acircuit which is formed on a substrate and includes the wire and a thinfilm transistor; a contact hole on the wire; an insulating bank coveringan end portion of the first lower electrode and an end portion of thesecond lower electrode, the insulating bank is formed on the flatteningfilm among the lower electrode, the first organic layer, and the upperelectrode; a first organic layer between the upper electrode and thefirst lower electrode, or between the upper electrode and the secondlower electrode, the first organic layer includes at least one layer ofan electron injection layer, a hole transport layer and a light emittinglayer; and a second organic layer between the upper electrode and thewire, the second organic layer includes the same layer as the at leastone layer which are included in the first organic layer, wherein theinsulating bank isolates each of the first lower electrode and thesecond lower electrode, the upper electrode is in contact with the wirethrough the contact hole opened in the flattening film and theinsulating bank, the first organic layer and the second organic layerare not in contact with each other, the second organic layer is incontact with a part of the wire in the contact hole, and the upperelectrode is in contact with the other part of the wire in the contacthole.
 2. The organic EL display device according to claim 1, wherein theupper electrode continuously is in contact with the wire within thedisplay region along the wire.
 3. The organic EL display deviceaccording to claim 1, wherein the wire runs along a plurality of sidesof the first lower electrode and the second lower electrode.
 4. Theorganic EL display device according to claim 3, wherein the contact holeis formed along a plurality of sides of the first lower electrode andthe second lower electrode.
 5. The organic EL display device accordingto claim 3, wherein the wire vertically and horizontally runs so as tosurround each of the first lower electrode and the second lowerelectrode.
 6. The organic EL display device according to claim 5,wherein the contact hole is formed vertically and horizontally so as tosurround each of the first lower electrode and the second lowerelectrode.